docs: def is_valid_field_name(value):
      """Ensure field name is valid."""
      leftovers = re.sub(r"\w", "", value)
      leftovers = re.sub(r"-", "", leftovers)
      if leftovers != "" or value[0].isdigit() or value[0] in ["-", "_"] or " " in value:
          return False
      return True